The invention is directed to a communication switching system In particular, it is directed to a switching system composed of a performance characteristics system and a base switching system.
Contemporary switching systems support a plurality of performance characteristics. These are auxiliary telecommunication services such as, for example, call redirection, conference service, hold for inquiry, hold, etc. Performance characteristics are realized in processor-controlled switching systems within the switching control procedures. These switching control procedures, also called switching software, contain the call control as well as the performance characteristics. The performance characteristics are thereby meshed with the call control as well as with one another. This leads to a high software complexity, the software structure thus becoming inflexible with respect to the introduction of new performance characteristics. In order to shorten the long introduction times for new performance characteristics caused as a result thereof, it has been considered to realize the parts of the control procedures that were hitherto dependent on one another separately in independent modules that respectively have a fixed interface toward the outside. Initial steps for separating the performance characteristics control from the switching control are pursued in the framework of the standardization procedures "Intelligent Network" at ITU-T SG 11 concerned with intelligent networks. In this respect, see the guidelines of the CCITT, "New Recommendation Q.1214. Distributed Functional Plane for Intelligent Network CS-1, COM XI-R212-E, pages 7 though 69 as well as annex pages 7 through 9.
A cleanly structured switching architecture arises by decoupling the performance characteristics control from the switching control, which is thereby reduced to its basic functionality. This is very modularly constructed and allows the fast introduction of new performance characteristics. The separation of the performance characteristics also enables development independent of the performance characteristics and the call control.
Such a structure divides a switching system or, respectively, the switching software into a base switching system and a performance characteristics system. The main components of a base switching system are a call controller, a database and a plurality of performance characteristics control modules. The call control is reduced to its basic tasks, the setup and cleardown of connections or, respectively, calls and is therefore referred to as basic call control. The performance characteristics control modules thereby form a set of functions via which the call objects of call, subscriber and connection can be accessed, via which, thus, calls can be manipulated.
The performance characteristics themselves are contained in the performance characteristics system that communicates with the base switching system via a protocol.
The basic call controller of the base switching system has the job of implementing the setup and cleardown of calls or, respectively, their appertaining connections according to subscriber requests. In the framework of its normal execution, consequently, it handles a two-party call. Over and above this, mechanisms are provided for reporting certain events to the performance characteristics control. Without influencing the performance characteristics system, the base switching system can control a call between two subscribers, i.e. it is autonomous with respect to the setup and cleardown of two-party calls. A two-party call exists between two communication terminal equipment respectively allocated to subscriber line units with a respective connection that produces the reference between a communication terminal equipment and the call. Each connection has a respective automatic status unit allocated to it as automatic status unit of the connection. The connections are linked to one another via the call.
Specific transitions that are triggered due to external events occur between the statusses of the automatic status units. Such events are subscriber/network messages or internal messages, namely messages between the two connections of a call.